The present invention relates in general to pressure sensors and, more particularly, to an electronic pressure sensor with the sensing die protected from hostile environments by a hermetically sealed stress isolated platform.
By 1996, federal government regulations will require that automotive fuel system vapor pressure sensors be placed in every automobile and light truck sold in the United States. The petrochemical environment of a fuel system is extremely hostile. It is known that mechanical pressure sensors can be manufactured to be impervious to adverse chemical environments. However, the mechanical sensor is very expensive and characterized by a bulky metallic package with a strain gauge-piezoelectric sensor. The size and cost of such a sensor make it impractical for use in automotive applications.
Due to cost, size, and reliability advantages of integrated electronics, it is desirable to adapt electronic sensor technology to petrochemical environments in automobile applications. Electronic pressure sensors are used in ambient and atmospheric applications. However, adaptation of electronic pressure sensors to petrochemical environments presents new problems to the technology. One such problem lies in the integrity of the sensor associated interconnects. Present uses of electronic pressure sensors permit intimate contact between sensor wirebonds, package leads, and the sensed non-hostile pressure medium. Any contact with hostile chemicals has proven to cause premature failure of the sensor.
It is further desired to extend electronic pressure sensor technology to higher pressure applications involving gases. In this instance, the fragile nature of the sensing die and interconnects creates stress problems that often lead to untimely failure of the sensor.
Hence, a need exists for a low cost and reliable hermetically sealed pressure sensor that can be used in hostile chemical and pressure environments.